Experimental study on water-gas permeability of high-temperature and high-pressure sandstone gas reservoirs in yingqiong basin

The water-gas relative permeability curve is one of the primary references used in the design of gas reservoir devel-opment schemes, dynamic analysis, index prediction, and gas-water distribution studies. In this work, we conducted water-gas relative permeability experiments under normal temperature (20C) and pressure (0.101 MPa) and high -temperature (135C) and high-pressure (75 MPa) conditions, targeting three rock samples with good physical proper-ties taken from the main production layer in the Yingqiong Basin. Mercury intrusion porosimetry and X-ray diffrac-tion experiments were introduced to explore the relationship between the experimental conditions and the gas-water relative permeability. It was understood that the temperature and pressure influence the water-gas seepage character-istics, mainly by changing the fluid properties and the microstructure of the rocks. The relative permeability curves under different temperatures and pressures demonstrated significant differences. Compared to the normal conditions, under high-temperature and high-pressure conditions the irreducible water saturation was lower, the two-phase co -permeation region was larger, and the isotonic point moved to the left. The relative permeability curves were related to the mineral composition and microstructure but had no direct relation with the permeability. At higher clay con-tent, the irreducible water saturation and residual gas saturation were higher and the two-phase co-permeation area was smaller. At larger throat radii of the rock samples, the irreducible water saturation and residual gas saturation decreased and the gas-water co-permeation area increased.